Strength calculations of threaded spindle.

I have to assess the sizing of a spindle of a DN600 Knife gate valve.
The spindle is subjected to two sources of loading acting in both shear and tensile.
•Torque applied to the spindle.
•Resulting thrust from line pressure.

Maximum shear stress
Because bending is involved, the shear stress distribution is not uniform; it occurs at the centre of the thread and is 50% higher than the average stress. At this point the bending stress is zero because maximum bending stress occurs at the outer fibres.
Tau_max=1.5F⁄bh

Buckling calculations
Because the load in the spindle is compressive when the blade of the valve bottoms out, the spindle is effectively a column and the possibility of buckling should be checked.

We assume that the spindle is flexible (pinned to blade) at one point and rigid at the other point. As per Mechanical Design Manual February 1999, the relationship between effective length Le and actual length La should be Le: 0.85La.

In this knife gate valve the blade bottoms out on the body casting, so I recommended that if the company are to fit an electric actuator that they make sure the torque settings and sizing of the actuator is set to the correct values to make sure that if the stroke has not been set right that the actuator does not exceed the maximum torque allowed without buckling...

From the calculations the spindle should be adequate to transfer the required torque and resulting thrust with a minimum safety factor of 2.45.

I know it is a lot to check but is someone would please help me check this it would be much apreciated, I am only in my 2nd year of working so would like some experienced input.